The major difference in ascorbate metabolism between the guinea pig and man is in excretory routes. The guinea pig excretes most of a labelled dose of ascorbate as respiratory CO2 whereas the urine is essentially the sole route of excretion in man. Experiments have demonstrated rapid and extensive decarboxylation of ascorbic acid by cecal microflora in the guinea pig and the secretion of 14C into the gut following intraperitoneal injection of (1-14C) ascorbic acid. An investigation of ascorbate metabolism in germfree guinea pigs has demonstrated a significant endogenous decarboxylation of the vitamin, although the amount decarboxylated was significantly less than in conventional animals. Biliary ascorbate was markedly elevated in germfree guinea pigs which suggests the liver as a major site for ascorbate decarboxylation. Additional experiments will explore the physiological significance of biliary ascorbate secretion and metabolism. An investigation of ascorbate kinetics in specific tissues revealed four tissue subgroups which differ distinctly in the rate of ascorbate uptake and turnover. These results provide a more comprehensive understanding of the physiological basis of the rapidly-and slowly-miscible ascorbate pools as described by the plasma ascorbate specific activity decay curve. After further validation of total body ascorbate kinetic methods, the influence of dietary ascorbic acid intake and physiological stress upon ascorbic acid turnover and pool size(s) will be investigated.